Firefighters check for hot spots in the forests above West Kelowna, B.C., on Tuesday. (CBC)

Hundreds of forestry jobs may have been lost as a result of the largest of three fires burning in B.C.'s Okanagan's Valley, which destroyed thousands of truckloads of timber — and the damage is not finished yet.

The Terrace Mountain fire has been burning in a steep mountain area north of West Kelowna since Saturday, and firefighters say the rugged terrain has been impossible to attack from the ground and difficult to tackle from the air, even at the best of times.

After strong winds fanned the flames on Monday, the fire grew to 13 square kilometres by some estimates, and firefighters say after three days, they still have only 20 per cent of the fire contained.

'If it hadn't burned ... potentially we would have ... 2,000 truckloads come out of an area like that.'— Murray Wilson, Tolko Industries Okanagan Woodlands Manager

And while the fire is still several kilometres away from any homes, officials have warned a handful of homeowners near the community of Fintry, about 40 kilometres north of West Kelowna, to be ready to leave on short notice as the wildfire continues to grow.

But mill operators are now concerned about the number of jobs that might be lost as the timber supply for four local sawmills goes up in flames.

Four mills affected

It is not clear how many jobs could be affected, but already, about 25 log haulers are off work, waiting for the fires to die down, according to Murray Wilson, the Okanagan woodlands manager for Tolko Industries.

"If it hadn't burned ... potentially we would have ... 2,000 truckloads come out of an area like that," said Murray on Tuesday. "We have four mills in the Okanagan, and it's a big part of supplying the wood for those mills."

Thick smoke kept firefighting helicopters grounded on Tuesday morning, making it hard to determine just how much timber has already been destroyed.

B.C.'s forestry industry is already in a severe downturn, with thousands of workers laid off in recent years and dozens of mills closing because of falling timber prices. The fire damage is just more bad news, Wilson said.

"We're dealing with mountain pine beetle and very tough economic conditions in our industry ... Anything that impacts that further is, obviously, a big negative for us and our contractors and the people that work for us," he said.

6,000 residents return home

Two other fires just to the south of Terrace Mountain in the Rose Valley and Glenrosa areas of West Kelowna have still not been contained by firefighters, but about half of the 11,000 residents of those areas who were forced out of their homes were allowed to return home.

About 60 per cent of the Glenrosa fire and about 10 per cent of the Rose Valley fire were contained on Tuesday, but evacuation alerts still remain in place.

Highways 97 and 97c were also re-opened on Tuesday morning, and Premier Gordon Campbell was expected to tour the area on Tuesday afternoon.